1. Field of the Invention
The present invention relates generally to light fixtures and devices used therein to prevent water intrusion into the more water sensitive areas of a light fixture. In particular, the present invention relates to sealing mechanisms utilized in housings for in-grade or below grade light fixtures to prevent water from entering the electrically sensitive areas of the light fixture. In even more particularity, the present invention relates to a hydrological barrier plate that interacts with a light fixture housing to prevent water from entering water sensitive areas of the light fixture.
2. Description of the Related Art
There are many types of light fixtures that are used for many different purposes, including indoor and outdoor illumination and decoration. One type of light fixture is commonly referred to as an in-grade light fixture due to all or part of the light fixture being located in the ground at or slightly above the level of the ground surface, whether earth or covered ground surfaces such as concrete, asphalt, wood or the like. Typically, these light fixtures are used to illuminate walls, columns, flags, trees, signs and other objects. A recessed in-grade light fixture can be used to illuminate a path along the ground and the area near the path. The typical in-grader light fixture has a glass lens component which is attached to the top of a housing that contains the various electrical components that are used to power and operate the lamp portion of the light fixture within the housing. Another type of light fixture having an underground component utilizes a mounting system mounted to the top of the below ground housing. The mounting system is connected to a separate lamp housing, usually allowing pivotal rotation of the lamp housing to aim the lamp at a desired location. Both of these types of fixtures can utilize housings that are configured to contain a power supply, power converters, transformers, aiming brackets for the lamp and other components. In order to hold all these materials, the housings extend relatively deep (i.e., 14 to 16 inches) into the ground. The housing may be configured into separate compartments for the various internal components.
As is known in the art, the electrical power for operating the lamps and light fixture components is typically brought to the underground housing by wiring contained in an outer protective conduit line that attaches to the housing at a junction box having a wiring compartment for wiring the light fixture to the supply of electricity. Ideally, the conduit lines are sealed from the environment so water cannot enter into the conduit such that when the conduit is connected to the housing, the system is sealed against water intrusion into the junction box and the remaining housing. However, as is well known by those in the lighting industry, water still finds a way into the junction box and the remaining housing. Installation problems, kinks in the conduit shielding or other problems allow water to migrate inside the conduit and wick along the wire to the junction box and then collect inside the housing. The most common problems resulting from water inside the housing include corrosion, electrical shorts, shortened life of the ballast (power converter) or transformer and shortened lamp life. In addition, water entry into the electrically sensitive areas can create risk of electrocution for those working on the housing.
The typical in-grade light fixture housing is designed to have the conduit attach to the housing at a junction box compartment that is located at or near the bottom of the housing or to the side of the housing. The wires from the conduit enter into-the junction box, which can be the lower compartment of a vertical configured housing or a separate side housing out-side the primary housing. Although the junction box of the typical in-grade fixture is designed to be hydrologically isolated from the remaining housing, water is generally able to enter the junction box and the primary compartment of the housing. Depending on the design of the components inside the housing, this invasion of water can damage the more sensitive electrical components contained therein. The typical mechanism for water to enter the primary compartment of the housing is for the water to wick along the wires and past any devices used to isolate the junction box compartment.
To avoid these problems, most light fixture manufacturers utilize, either singularly or in combination, “watertight” wire connectors for connecting the wires together in the junction box compartment and/or sealing compound around the wires in the junction box compartment. Some light fixture manufacturers utilize a “watertight” wire or cord connector that is designed to prevent water from moving along the outside of the wire. Unfortunately water is usually still able to enter the primary compartments via the wire, typically inside the wire (which the connector is not designed to prevent) along the cardboard packing material used inside the wire insulation. Other light fixture manufacturers recommend the person installing the light fixture pour a “sealing compound”, such as silicon potting compound, around the wires in the junction box to encase the wires in the compound so as to prevent water from passing through the junction box into the primary housing compartment. Problems with these compounds include having to rely on the contractor to accurately and properly place the compound to obtain an effective sealing and the likelihood that there will be air pockets inside the junction box that will allow water to pass.
The typical cover plate utilized to seal off the junction box compartment from the primary compartment is threaded into or attached to (i.e., with screws or other connectors) the housing and has one or more sealing mechanisms, such as o-rings or gaskets, near the outer edge of the cover plate and a wire pass-through device to allow the electrical power to pass to the components in the primary housing compartment. Heretofore, the o-rings or gaskets used to provide the seal between the cover plate and the housing are axially compressed by the action of the threads or connectors used to connect the cover plate to the housing. One major disadvantage of this type of sealing mechanism is that the effectiveness of the seal is dependent on the person threading or attaching the cover plate to the housing. If the cover plate is not properly threaded or attached, it will fail to prevent water passage into or from the junction box. Another disadvantage of the typical in-grade light fixture housing is that it can be very difficult to properly thread or attach the cover plate to the housing and very difficult to ensure that a proper seal is obtained. The inventors are aware of some manufacturers that utilize up to ten o-rings to obtain the desired seal. Despite this effort, water still wicks along the wire from the junction box compartment into the primary compartment.
Although the goal of in-grade light fixtures is to have the junction box compartment remain dry, generally all light fixture manufacturers know that in reality some amount of water will likely get inside that compartment due to a failure to completely seal the conduit system. As a result, the real goal is to prevent any water that collects inside the junction box from invading the other, more sensitive areas of the light fixtures where it can cause immediate or long term damage. As described above, the known existing art show the broad concept of attempting to prevent water intrusion into the primary housing compartments. For any housing to effectively keep water out of the housing, it must utilize a relatively simple to use and cost efficient mechanism. None of the known light fixture housing or sealing devices, whether individually or in all appropriate combinations, comprise a relatively inexpensive to manufacture, easy to operate and fully effective mechanism of keeping water from the primary compartments of a light fixture housing. Specifically, the known prior art does not disclose a sealed in-grate light fixture or a hydrological barrier plate that prevents water intrusion into the primary housing compartment. What is needed is a housing that is more effective at preventing water intrusion into the primary electrical compartments of the housing and a hydrological barrier plate for use in such a housing that effectively stops water from passing from the junction box to the primary housing compartments.